/*
 *  Platform-specific and custom entropy polling functions
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 *
 *  This file is provided under the Apache License 2.0, or the
 *  GNU General Public License v2.0 or later.
 *
 *  **********
 *  Apache License 2.0:
 *
 *  Licensed under the Apache License, Version 2.0 (the "License"); you may
 *  not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *  http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 *  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *  **********
 *
 *  **********
 *  GNU General Public License v2.0 or later:
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 *  **********
 */

#if defined(__linux__) && !defined(_GNU_SOURCE)
/* Ensure that syscall() is available even when compiling with -std=c99 */
#define _GNU_SOURCE
#endif

#if !defined(MBEDTLS_CONFIG_FILE)
#include "nettls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif

#include <string.h>

#if defined(MBEDTLS_ENTROPY_C)

#include "nettls/entropy.h"
#include "nettls/entropy_poll.h"

#if !defined(MBEDTLS_NO_PLATFORM_ENTROPY)

#if !defined(unix) && !defined(__unix__) && !defined(__unix) && !defined(__APPLE__) && !defined(_WIN32) && !defined(__QNXNTO__) && !defined(__HAIKU__)
#error "Platform entropy sources only work on Unix and Windows, see MBEDTLS_NO_PLATFORM_ENTROPY in config.h"
#endif

#if defined(_WIN32) && !defined(EFIX64) && !defined(EFI32)

#if !defined(_WIN32_WINNT)
#define _WIN32_WINNT 0x0400
#endif
#include <windows.h>
#include <wincrypt.h>

int mbedtls_platform_entropy_poll(void* data, unsigned char* output, size_t len, size_t* olen)
{
    HCRYPTPROV provider;
    ((void)data);
    *olen = 0;

    if (CryptAcquireContext(&provider, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT) == FALSE) {
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
    }

    if (CryptGenRandom(provider, (DWORD)len, output) == FALSE) {
        CryptReleaseContext(provider, 0);
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
    }

    CryptReleaseContext(provider, 0);
    *olen = len;

    return (0);
}
#else /* _WIN32 && !EFIX64 && !EFI32 */

/*
 * Test for Linux getrandom() support.
 * Since there is no wrapper in the libc yet, use the generic syscall wrapper
 * available in GNU libc and compatible libc's (eg uClibc).
 */
#if defined(__linux__) && defined(__GLIBC__)
#include <unistd.h>
#include <sys/syscall.h>
#if defined(SYS_getrandom)
#define HAVE_GETRANDOM
#include <errno.h>

static int getrandom_wrapper(void* buf, size_t buflen, unsigned int flags)
{
    /* MemSan cannot understand that the syscall writes to the buffer */
#if defined(__has_feature)
#if __has_feature(memory_sanitizer)
    memset(buf, 0, buflen);
#endif
#endif
    return (syscall(SYS_getrandom, buf, buflen, flags));
}
#endif /* SYS_getrandom */
#endif /* __linux__ */

#include <stdio.h>

int mbedtls_platform_entropy_poll(void* data, unsigned char* output, size_t len, size_t* olen)
{
    FILE* file;
    size_t read_len;
    int ret;
    ((void)data);

#if defined(HAVE_GETRANDOM)
    ret = getrandom_wrapper(output, len, 0);
    if (ret >= 0) {
        *olen = ret;
        return (0);
    } else if (errno != ENOSYS)
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
        /* Fall through if the system call isn't known. */
#else
    ((void)ret);
#endif /* HAVE_GETRANDOM */

    *olen = 0;

    file = fopen("/dev/urandom", "rb");
    if (file == NULL)
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);

    read_len = fread(output, 1, len, file);
    if (read_len != len) {
        fclose(file);
        return (MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
    }

    fclose(file);
    *olen = len;

    return (0);
}
#endif /* _WIN32 && !EFIX64 && !EFI32 */
#endif /* !MBEDTLS_NO_PLATFORM_ENTROPY */

#if defined(MBEDTLS_TEST_NULL_ENTROPY)
int mbedtls_null_entropy_poll(void* data, unsigned char* output, size_t len, size_t* olen)
{
    ((void)data);
    ((void)output);
    *olen = 0;

    if (len < sizeof(unsigned char))
        return (0);

    *olen = sizeof(unsigned char);

    return (0);
}
#endif

#endif /* MBEDTLS_ENTROPY_C */
